Somebody said:
As a former investor, an entrepreneur that thinks he/she understands my business better than I do is a big red flag.
and I replied:
As an entrepreneur, an investor that thinks he/she understands my business better than I do is a big red flag.
To me, this gets to (or near) the heart of the thing. If you're a VC / angel, you're probably fairly smart, probably well connected, and probably have a modest amount of interesting experience in many things. But if you're not one of the VC / angel types who came from a background as an entrepreneur, why should I believe that you have much knowledge that will be specifically relevant to my business. And why should I think you are particularly well suited to judge my business?
msuster, sgblank, pg, and a few others, I would put a lot of faith in, based on their backgrounds... but most other VCs, I really wouldn't be looking to them for much besides: A. money and B. introductions / referrals. I almost certainly wouldn't be looking for product advice or marketing strategy, etc. from them (unless they had some proven background in that area).